Pickled onion: Pickled onions are a food item consisting of onions pickled in a solution of vinegar and salt, often with other preservatives and flavourings. There is a variety of small white pickled onions known as 'silverskin' onions; due to imperfections they are pickled instead of being wasted. They are frequently used as an essential component of the Martini cocktail variant known as a Gibson. Pickled onions are usually pickled in malt vinegar and the onions are about 25 millimetres (1 in) in diameter. Silverskin onions are pickled in white vinegar, and are much smaller. Full sized onions, e.g., Spanish onions, can be pickled if sliced first.